The development of floating, anchored wind turbines that can be used at great depths will strongly enhance access to areas for the expansion of wind energy at sea. Current technology for wind turbines located at sea is considerably limited to permanently installed towers at low depths, under approximately 30 m.
Permanent installations at depths over 30 m generally result in technical problems and high costs. This has meant that, until now, sea depths of more than around 30 m have been regarded as technically and commercially unfavourable for the installation of wind turbines.
With floating solutions at greater sea depths, the foundation problem and costs associated with complicated, labour-intensive installations can be avoided.
A wind turbine that is mounted on a floating foundation will move on account of the forces from the wind and waves. A good wind turbine foundation design will ensure that the system's eigenperiods for rigid cell movements (surge, sway, heave, roll, pitch and yaw) are outside the period range for sea waves, which is approximately 5-20 seconds.
There will still be forces that act in connection with the eigenperiods for the system (swell, non-linear wave forces, fluctuations in wind speed, current forces, etc.). If such forces are not to produce unacceptable movements, they must not be too large, and the system must have damping for the relevant periods.